A chitosan-ferroferric oxide-rare earth cerium composite material, a preparation method and application thereof

Abstract

This invention relates to the field of composite material technology, specifically to a chitosan-ferric oxide-rare earth cerium composite material, its preparation method, and its applications. The chitosan-ferric oxide-rare earth cerium composite material of this invention consists of a chitosan matrix framework, a magnetic component of ferric oxide, and a cerium-containing structural modification component, distributed in an irregular block shape with cerium-containing particles distributed on the surface. Ferric oxide is generated in situ and dispersed within the chitosan matrix framework, while the cerium-containing structural modification component mainly binds to the hydroxyl, amino, and amide groups on the chitosan molecular chain through coordination. The chitosan-ferric oxide-rare earth cerium composite material of this invention exhibits excellent heavy metal ion adsorption and magnetic separation performance. It not only overcomes the shortcomings of existing technologies, such as difficulty in adsorbent separation and recovery, easy dissolution and weight loss under acidic conditions, and poor treatment effect of heavy metal wastewater, but also solves the problems of limited adsorption capacity, insufficient mechanical strength, and difficulty in reusing single chitosan materials.

Description

Technical Field

[0001] This invention relates to the field of composite material technology, specifically to a chitosan-iron tetroxide-rare earth cerium composite material, its preparation method, and its application. Background Technology

[0002] Currently, the main methods for treating heavy metal wastewater include ion exchange, electrolysis, and chemical precipitation. However, these methods generally suffer from drawbacks such as complex processes, high operating costs, and poor treatment efficiency for low-concentration wastewater. In contrast, adsorption methods utilize the special structure and surface properties of adsorbents to immobilize heavy metal ions on the adsorbent surface through physical and chemical adsorption, thereby achieving effective removal of heavy metal ions. Currently, the development of high-performance, low-cost adsorbents has become a key research direction in adsorption methods to further improve their feasibility and effectiveness in practical applications.

[0003] Chitosan is a natural polymer containing hydroxyl and amino groups, exhibiting excellent chelation and adsorption capabilities for various heavy metal ions. It also boasts advantages such as good biocompatibility, biodegradability, and wide availability. However, chitosan also suffers from drawbacks, including relatively weak mechanical strength, easy solubility in acidic media, limited adsorption capacity, and difficulties in separation and recovery. While chitosan-Fe3O4 composite magnetic materials, formed by surface modification or coating of Fe3O4 with chitosan, have addressed the separation and recovery difficulties to some extent, these materials still suffer from structural instability under acidic conditions, limited adsorption active sites, and poor reusability. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a chitosan-iron tetroxide-rare earth cerium composite material, its preparation method, and its application. The chitosan-iron tetroxide-rare earth cerium composite material of this invention is composed of a matrix framework of chitosan, a magnetic component of iron tetroxide, and a cerium-containing structural modification component, and it has excellent heavy metal ion adsorption and magnetic separation performance. In this process, ferric oxide is generated in situ and dispersed in the chitosan matrix, endowing the chitosan-ferric oxide-rare earth cerium composite material with superparamagnetic and magnetic response separation capabilities, overcoming the shortcomings of existing technologies such as difficult adsorbent separation and recovery and high operating costs. The cerium-containing structural modification component combines with the amino or hydroxyl groups on the chitosan molecular chain through coordination, strengthening the cross-linked network structure and significantly improving the mechanical strength and acid resistance of the chitosan-ferric oxide-rare earth cerium composite material. This solves the problems of insufficient mechanical strength, poor chemical stability, and difficulty in reusing chitosan and chitosan-modified ferric oxide materials. At the same time, new heavy metal ion adsorption active sites are introduced on the surface of the chitosan-ferric oxide-rare earth cerium composite material, synergistically improving the adsorption capacity and selectivity of the chitosan-ferric oxide-rare earth cerium composite material. This solves the technical problems of limited adsorption capacity and low removal efficiency of heavy metal ions in existing single chitosan materials and chitosan-modified ferric oxide materials.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first objective of this invention is to provide a chitosan-iron oxide-rare earth cerium composite material, which is composed of a chitosan matrix skeleton, an iron oxide magnetic component, and a cerium-containing structural modification component. The chitosan-iron oxide-rare earth cerium composite material is distributed in an irregular block shape, with cerium-containing particles distributed on the surface. The iron oxide is generated in situ and dispersed in the chitosan matrix skeleton, and the cerium-containing structural modification component mainly binds to the hydroxyl, amino, and amide groups on the chitosan molecular chain through coordination.

[0006] Among them, iron oxide imparts superparamagnetism and magnetic separation ability to chitosan-iron oxide-rare earth cerium composite material; the cerium-containing structural modification component strengthens the cross-linking network, inhibits acid dissolution, and provides active sites for heavy metal adsorption.

[0007] Preferably, the cerium-containing structural modification component is a mixture of cerium oxide and cerium hydroxide.

[0008] The second objective of this invention is to provide a method for preparing the above-mentioned chitosan-ferric oxide-rare earth cerium composite material, comprising the following steps: S1. Dissolve chitosan in water containing glacial acetic acid to obtain a chitosan solution.

[0009] S2. Dissolve soluble ferrous salt, soluble ferric salt and soluble cerium salt together in water to obtain a mixed metal salt solution; add the mixed metal salt solution to the chitosan solution, and the metal ions in the mixed metal salt solution undergo a coordination reaction with the amino and hydroxyl groups of chitosan to obtain a chitosan-metal ion complex solution.

[0010] S3. Add the chitosan-metal ion complex solution dropwise to the sodium tripolyphosphate aqueous solution. The polyvalent phosphate in the sodium tripolyphosphate reacts with the protonated amino groups (-NH3) of chitosan through electrostatic interaction. + Ionic cross-linking occurs, forming a three-dimensional network structure; on the other hand, phosphate groups coordinate with metal ions in the chitosan-metal ion complex, fixing the metal ions in the three-dimensional network. Through the above synergistic mechanism, cross-linked products are obtained.

[0011] S4. The cross-linking product is placed in an alkaline solution for precipitation. During the precipitation reaction, Fe in the cross-linking product... 2+ and Fe 3+ With OH - Combined, it undergoes heating and dehydration to form Fe3O4; simultaneously, Ce... 3+ With OH - By combining the formation of cerium hydroxide precipitate and partially converting it into cerium oxide, a chitosan-iron tetroxide-rare earth cerium composite material is obtained.

[0012] Preferably, the mass ratio of chitosan, soluble ferric salt, soluble ferrous salt, and soluble cerium salt is 1:1.2~1.5:0.9~1.1:0.15~0.25. When the amount of iron salt (i.e., soluble ferric salt and soluble ferrous salt) is too small, the amount of Fe3O4 generated is insufficient, leading to a weakened magnetic responsiveness and reduced magnetic separation efficiency of the chitosan-ferric oxide-rare earth cerium composite material. When the amount of iron salt is too large, Fe3O4 particles are prone to agglomeration, blocking the pore structure of the chitosan-ferric oxide-rare earth cerium composite material. When the amount of soluble cerium salt is too small, its modification effect on the chitosan cross-linking network is weak, and the heavy metal adsorption enhancement effect is not significant. When the amount of soluble cerium salt is too large, the generated Ce(OH)3 or CeO2 is prone to agglomeration, resulting in a reduction of effective adsorption active sites and thus reducing adsorption performance.

[0013] Preferably, the soluble trivalent iron salt is Fe2(SO4)3, the soluble divalent iron salt is FeSO4·7H2O, and the soluble cerium salt is cerium acetate.

[0014] Preferably, the mass ratio of chitosan to sodium tripolyphosphate is 1:2.5~3. When the amount of sodium tripolyphosphate is too small, the chitosan cross-linking is incomplete, resulting in a loose three-dimensional network structure with insufficient mechanical strength and easy loss of metal ions. When the amount of sodium tripolyphosphate is too large, the chitosan cross-linking is excessive, and the amino groups on the molecular chain are over-occupied, leading to a reduction in the number of active sites for heavy metal adsorption and a decrease in adsorption performance.

[0015] Preferably, the cross-linking reaction is carried out under stirring at room temperature for 30 to 40 minutes. If the time is too short, the cross-linking reaction will be incomplete.

[0016] Preferably, the precipitation reaction conditions are: stirring at 90℃~100℃ for 100min~150min.

[0017] A third objective of this invention is to provide the application of the above-mentioned chitosan-iron tetroxide-rare earth cerium composite material in the preparation of heavy metal ion adsorbents.

[0018] Preferred application method: Chitosan-Fe3O4-Rare Earth Cerium composite material was added to a Pb-containing... 2+ Adsorption occurs in an aqueous solution containing Pb; wherein, the chitosan-iron tetroxide-rare earth cerium composite material is used in conjunction with Pb-containing... 2+ The aqueous solution has a mass-to-volume ratio of 5 mg to 150 mg: 25 mL and contains Pb. 2+ In aqueous solution, Pb 2+ The mass concentration is 15 mg / L to 150 mg / L.

[0019] Preferably, the adsorption conditions are: containing Pb 2+ The pH value of the aqueous solution is 3~6, ​​and it is adsorbed at 25℃~45℃ for 5min~120min.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention provides a chitosan-ferric oxide-rare earth cerium composite material, which is composed of a chitosan matrix framework, a magnetic component of ferric oxide, and a cerium-containing structural modification component. The chitosan-ferric oxide-rare earth cerium composite material is irregularly distributed in blocks, with cerium-containing particles distributed on the surface. Ferric oxide is generated in situ and dispersed within the chitosan matrix framework, while the cerium-containing structural modification component binds to the hydroxyl, amino, and amide groups on the chitosan molecular chain through coordination. The chitosan-ferric oxide-rare earth cerium composite material of this invention exhibits excellent heavy metal ion adsorption and magnetic separation performance. It not only overcomes the shortcomings of existing technologies, such as difficulty in adsorbent separation and recovery and easy dissolution and weight loss under acidic conditions, but also solves the technical problems of limited adsorption capacity and low heavy metal ion removal efficiency of existing single chitosan materials and chitosan-modified ferric oxide.

[0021] The abundant hydroxyl and amino groups on the chitosan molecular chain provide chelation adsorption sites for heavy metal ions. The cerium-containing structural modification components combine with the amino or hydroxyl groups on the chitosan molecular chain through coordination, optimizing the cross-linking network structure. On the one hand, this inhibits the dissolution of chitosan in acidic media, improving the structural stability and acid resistance of the chitosan-ferric oxide-rare earth cerium composite material. On the other hand, it introduces new active sites for heavy metal ion adsorption, enhancing the adsorption capacity and selectivity of the chitosan-ferric oxide-rare earth cerium composite material for heavy metal ions. Ferric oxide is generated in situ and dispersed in the chitosan matrix, giving the chitosan-ferric oxide-rare earth cerium composite material superparamagnetism, enabling it to achieve rapid solid-liquid separation under the action of an external magnetic field, facilitating recycling and regeneration.

[0022] 2. This invention also provides a method for preparing a chitosan-ferric oxide-rare earth cerium composite material. Chitosan is dissolved in water containing glacial acetic acid to obtain a chitosan solution. A soluble ferrous salt, a soluble ferric salt, and a soluble cerium salt are dissolved together in water to obtain a mixed metal salt solution. The mixed metal salt solution is added to the chitosan solution, where the metal ions in the mixed metal salt solution coordinate with the amino and hydroxyl groups of chitosan to obtain a chitosan-metal ion complex solution. The chitosan-metal ion complex solution is added dropwise to an aqueous solution of sodium tripolyphosphate. Sodium tripolyphosphate forms a three-dimensional network through electrostatic interaction with chitosan, and simultaneously coordinates with the metal ions in the chitosan-metal ion complex through phosphate groups, fixing the metal ions in the three-dimensional network to obtain a crosslinked product. The crosslinked product is placed in an alkaline solution for precipitation. During the precipitation reaction, the Fe in the crosslinked product... 2+ and Fe 3+ With OH - Combined, it undergoes heating and dehydration to form Fe3O4; simultaneously, Ce... 3+ With OH - By combining the formation of cerium hydroxide precipitate and partially converting it into cerium oxide, a chitosan-iron tetroxide-rare earth cerium composite material is obtained.

[0023] The preparation method of this invention is simple and efficient. It achieves magnetic modification and rare earth modification simultaneously through in-situ precipitation and crosslinking, avoiding the cumbersome multi-step synthesis, and is easy to scale up industrially. Moreover, the resulting composite material has a stable structure and uniform properties.

[0024] 3. Using the chitosan-ferric oxide-rare earth cerium composite material prepared in this invention as an adsorbent, it is applied to the treatment of wastewater containing lead heavy metal ions. Through adsorption and magnetic separation processes, efficient removal of heavy metal ions and convenient recovery of the adsorbent are achieved. Under the conditions of pH 4-6, temperature 25℃-45℃, and adsorption time 60min-120min, the chitosan-ferric oxide-rare earth cerium composite material effectively removes lead heavy metal ions.2+ All of them exhibited excellent adsorption effects. Attached Figure Description

[0025] Figure 1 The image shows the SEM image of the chitosan-ferric oxide composite material of Comparative Example 1.

[0026] Figure 2 The image shows the SEM image of the chitosan-iron tetroxide-rare earth cerium composite material of Example 1.

[0027] Figure 3 The image shows the XPS high-resolution spectrum of the Ce 3d orbital of the chitosan-iron tetroxide-rare earth cerium composite material in Example 1.

[0028] Figure 4 The images show the XRD patterns of the chitosan-ferric oxide composite material of Comparative Example 1 and the chitosan-ferric oxide-rare earth cerium composite material of Example 1.

[0029] Figure 5 The images show the FTIR spectra of the chitosan-ferric oxide composite material of Comparative Example 1 and the chitosan-ferric oxide-rare earth cerium composite material of Example 1.

[0030] Figure 6 The graph shows the effect of pH on the adsorption performance of the chitosan-ferric oxide composite material in Comparative Example 1 and the chitosan-ferric oxide-rare earth cerium composite material in Example 1.

[0031] Figure 7 The graph shows the effect of adsorption time on the adsorption performance of the chitosan-ferric oxide composite material in Comparative Example 1 and the chitosan-ferric oxide-rare earth cerium composite material in Example 1.

[0032] Figure 8 The graph shows the effect of the amount of chitosan-ferric oxide composite material in Comparative Example 1 and the chitosan-ferric oxide-rare earth cerium composite material in Example 1 on the adsorption performance.

[0033] Figure 9 The graph shows the effect of temperature on the adsorption performance of the chitosan-ferric oxide composite material in Comparative Example 1 and the chitosan-ferric oxide-rare earth cerium composite material in Example 1.

[0034] Figure 10 The chitosan-iron tetroxide-rare earth cerium composite material of Example 1 is effective against Pb. 2+ The Langmuir adsorption isotherm model diagram.

[0035] Figure 11 The chitosan-ferric oxide composite material of Comparative Example 1 is effective against Pb. 2+ The Freundlich adsorption isotherm model diagram. Detailed Implementation

[0036] The technical solution of the present invention will be clearly and completely described below with reference to the data in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0037] It should be noted that the technical terms used in this invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of this invention. Unless otherwise specified, all raw materials, reagents, instruments and equipment used in the following embodiments of this invention can be purchased on the market or prepared by existing methods.

[0038] While chitosan-based adsorbents possess excellent heavy metal chelating capabilities, they generally suffer from drawbacks such as weak mechanical strength, easy solubility in acidic media, limited adsorption capacity, and difficulties in separation and recovery, severely restricting their practical application. Existing technologies utilize chitosan to modify or coat the surface of iron(III) oxide (Fe3O4) to form chitosan-Fe3O4 composite magnetic materials. Although this addresses the separation and recovery difficulties to some extent, it still suffers from structural instability under acidic conditions, limited adsorption active sites, and poor reusability, making it difficult to meet the needs of practical wastewater treatment.

[0039] This invention simplifies the recovery and regeneration of chitosan by imbuing it with magnetism using magnetic separation technology. Fe3O4 magnetic particles exhibit superparamagnetism; when combined with chitosan, the chitosan-Fe3O4-rare earth cerium composite material achieves rapid and convenient solid-liquid separation under an external magnetic field, significantly improving the ease of adsorbent recovery. Simultaneously, rare earth ions, due to their small ionic radius, high charge number, and ionic potential, exhibit unique structural characteristics and physicochemical properties, enabling them to coordinate with functional groups on the chitosan molecular chain, forming a more stable network structure. This cross-linking not only effectively inhibits the dissolution of chitosan in acidic environments but also introduces new adsorption active sites, further expanding the removal capacity of the chitosan-Fe3O4-rare earth cerium composite material for various pollutants.

[0040] Given the chelating adsorption properties of chitosan, the structural modification effect of rare earth ions, and the magnetic separation effect of Fe3O4 particles, this invention provides a chitosan-ferric oxide-rare earth cerium composite material, composed of a chitosan matrix, a magnetic component (ferric oxide), and a cerium-containing structural modification component. Chitosan, as the matrix material, provides abundant chelating adsorption sites for heavy metal ions; ferric oxide, as the magnetic component, endows the chitosan-ferric oxide-rare earth cerium composite material with superparamagnetism and magnetically responsive separation capabilities; the cerium-containing structural modification component, as the structural modification component, binds to the amino or hydroxyl groups on the chitosan molecular chain through coordination, strengthening the cross-linked network structure, improving the mechanical strength and acid resistance of the composite material, and simultaneously introducing new heavy metal ion adsorption active sites, synergistically enhancing adsorption capacity and selectivity.

[0041] To enable those skilled in the art to more clearly understand the technical solution of the present invention, the following will provide a detailed description in conjunction with specific embodiments: Example 1 A method for preparing a chitosan-iron tetroxide-rare earth cerium composite material includes the following steps: S1. Mix 1g of chitosan and 0.4mL of glacial acetic acid in 20mL of deionized water and stir at high speed until completely dissolved to obtain a chitosan mixed solution; dissolve 1.3g of Fe2(SO4)3, 0.97g of FeSO4·7H2O and 0.15g of cerium acetate together in 20mL of deionized water until completely dissolved to obtain a metal salt mixed solution; add the metal salt mixed solution to the chitosan mixed solution and stir continuously for 15min to obtain a chitosan-metal ion complex solution.

[0042] S2. The chitosan-metal ion complex solution was added dropwise to 50 mL of aqueous solution containing 3 g of sodium tripolyphosphate, and the mixture was stirred for 0.5 h before being filtered to obtain the cross-linked product residue. The cross-linked product residue was then poured into 75 mL of 1.5 mol / L NaOH solution, and the system was heated to 100 °C and reacted for 120 min. After the reaction was completed, the mixture was stirred until the solution cooled. The mixture was then filtered and washed until the filtrate was neutral. The residue was poured into a glass dish and dried at 60 °C for 24 h to obtain the chitosan-iron tetroxide-rare earth cerium composite material.

[0043] Example 2 A method for preparing a chitosan-iron tetroxide-rare earth cerium composite material is the same as that in Example 1, except that the mass ratio of chitosan, Fe2(SO4)3, FeSO4·7H2O and cerium acetate in S1 is replaced by 1:1.3:0.97:0.15 to 1:1.2:0.9:0.15, thus obtaining the chitosan-iron tetroxide-rare earth cerium composite material.

[0044] Example 3 A method for preparing a chitosan-iron tetroxide-rare earth cerium composite material is the same as that in Example 1, except that the mass ratio of chitosan, Fe2(SO4)3, FeSO4·7H2O and cerium acetate in S1 is replaced by 1:1.3:0.97:0.15 to 1:1.5:1.1:0.25 to obtain the chitosan-iron tetroxide-rare earth cerium composite material.

[0045] Example 4 A method for preparing a chitosan-iron tetroxide-rare earth cerium composite material is the same as the preparation method in Example 1, except that the amount of sodium tripolyphosphate added in S2 is replaced from 3g to 2.5g to obtain the chitosan-iron tetroxide-rare earth cerium composite material.

[0046] Comparative Example 1 A method for preparing a chitosan-ferric oxide composite material includes the following steps: 1 g of chitosan and 0.4 mL of glacial acetic acid were mixed in 20 mL of deionized water and stirred at high speed until completely dissolved to obtain a chitosan mixed solution; 1.3 g of Fe2(SO4)3 and 0.97 g of FeSO4·7H2O were dissolved together in 20 mL of deionized water to obtain a mixed solution; the mixed solution was added to the chitosan mixed solution and stirred continuously for 15 min to obtain a reaction solution.

[0047] S2. The reaction solution was added dropwise to 50 mL of aqueous solution containing 3 g of sodium tripolyphosphate, and stirred for 0.5 h. After filtration, the filter residue was poured into 75 mL of 1.5 mol / L NaOH solution. The system was heated to 100 °C and reacted for 120 min. After the reaction was completed, the mixture was stirred until the solution cooled. The mixture was then filtered and washed until the filtrate was neutral. The filter residue was poured into a glass dish and dried at 60 °C for 24 h to obtain the chitosan-iron oxide composite material.

[0048] A. Characterization: Depend on Figure 1 The results showed that the chitosan-ferric oxide composite material of Comparative Example 1 had an irregular blocky structure with a porous surface, which was conducive to the contact and adhesion of adsorbates. The presence of the porous structure also confirmed the successful realization of the cross-linking process.

[0049] Depend on Figure 2The results showed that the chitosan-ferric oxide-rare earth cerium composite material exhibited an irregular blocky distribution. Compared with the chitosan-ferric oxide composite material in Comparative Example 1, its surface lacked obvious pores but contained a large number of fine particles (Ce(OH)3 and CeO2 particles). The presence of these particles provided more active sites for adsorption and also helped to enhance the structural stability of the chitosan-ferric oxide-rare earth cerium composite material. The changes in surface morphology indicated that chitosan, rare earth cerium, and Fe3O4 particles were successfully composited.

[0050] Depend on Figure 3 The characteristic peaks at binding energies of approximately 903 eV, 885 eV and 900 eV, 881 eV correspond to Ce, respectively. 4+ and Ce 3+ The spin orbital splitting signal indicates that cerium in the chitosan-iron tetroxide-rare earth cerium composite material exists in a mixed valence state (Ce). 4+ and Ce 3+ It exists in the form of ).

[0051] exist Figure 4 In the studies, both the chitosan-ferric oxide (Fe3O4) composite material and the chitosan-ferric oxide-rare earth cerium composite material exhibited broadened diffraction peaks at 2θ = 20°, which are diffraction peaks formed by the regular crystallization of chitosan. The chitosan-ferric oxide-rare earth cerium composite material showed relatively obvious diffraction peaks at 2θ values ​​of 30.7°, 35.7°, 43.2°, 57.0°, and 62.9°, corresponding to the 220, 331, 400, 511, and 440 crystal planes of Fe3O4, respectively. While the chitosan-ferric oxide composite material also exhibited Fe3O4 diffraction peaks, the number of peaks was significantly fewer compared to the chitosan-ferric oxide-rare earth cerium composite material. This is mainly due to the greater amount of chitosan coating on the Fe3O4 surface, resulting in weaker diffraction peaks.

[0052] like Figure 5 As shown: Curve c (chitosan) is at 3394.1 cm⁻¹. -1 The peak for the -OH / -NH stretching vibration is shown at 2923.7 cm⁻¹. -1 The peak at 1650.2 cm⁻¹ represents the -CH₂ stretching vibration. -1 The peak at 1598.9 cm⁻¹ corresponds to amide I. -1 The location is the amide II band, 1077.2 cm. -1 The peak at 3428.9 cm⁻¹ represents the COC glycosidic bond, reflecting its polysaccharide structural characteristics; curve a (chitosan-ferric oxide composite material) has a peak at 3428.9 cm⁻¹. -1 The increased wavenumber of the -OH / -NH peak indicates that the magnetic particles disrupt hydrogen bonds, and the peak at 1073.1 cm⁻¹... -1The retention of the glycosidic bond peak indicates a stable backbone; curve b (chitosan-ferric oxide-rare earth cerium composite material) is at 3402.3 cm⁻¹. -1 The wavenumber of the -OH / -NH peak decreases to 1631.7 cm⁻¹. -1 The significant red shift of the amide I band confirms that cerium ions have strong coordination interactions with the hydroxyl, amino, and amide groups on the chitosan molecular chain, and that the band at 1075.1 cm⁻¹... -1 The presence of glycosidic bond peaks indicates that the chitosan backbone has not been damaged. Comparing the three curves, all retain glycosidic bond peaks, further confirming the integrity of the chitosan backbone. These changes in FTIR characteristic peaks fully demonstrate the successful composite material development of chitosan-ferric oxide-rare earth cerium. While magnetic modification and rare earth cerium composite did not destroy the chitosan backbone, they optimized adsorption and magnetic separation performance through functional group peak shifts and bonding interactions, providing spectroscopic evidence for material modification and adsorption mechanisms.

[0053] B. Application: ①The effect of pH value on adsorption effect: To investigate the effect of different pH values ​​on the adsorption efficiency of the adsorbent, 100 mL of Pb-containing solutions with a mass concentration of 25 mg / L and pH values ​​of 3, 4, 4.5, 5, and 6 were prepared. 2+ Each solution contains Pb 2+ 25 mL of the solution was transferred to an Erlenmeyer flask, and then 50 mg of chitosan-ferric oxide composite material and chitosan-ferric oxide-rare earth cerium composite material were weighed out and added to the Erlenmeyer flask as adsorbents. The Erlenmeyer flask was placed in a constant temperature shaker at 25℃ and shaken for 90 min. After shaking, the solution was filtered using a syringe with a filter membrane. The filtrate was retained and diluted with a standard curve for absorbance measurement. Based on the obtained data, the adsorption capacity and adsorption rate were calculated to obtain the adsorption capacity of chitosan-ferric oxide composite material and chitosan-ferric oxide-rare earth cerium composite material for Pb at different pH values. 2+ Adsorption effect.

[0054] like Figure 6 As shown, within the pH range of 3.0 to 5.0, the effect of chitosan-ferric oxide-rare earth cerium composite material on Pb increases with increasing acidity or alkalinity. 2+ The adsorption capacity showed an increasing trend, reaching its maximum at pH 5.0; however, when the pH further increased to 6.0, the adsorption capacity decreased significantly. Based on this experimental phenomenon, it was determined that the chitosan-ferric oxide-rare earth cerium composite material adsorbs Pb. 2+ The optimal pH value is 5.0.

[0055] ② The effect of adsorption time on adsorption performance: Prepare a solution containing Pb at pH 5 and a mass concentration of 25 mg / L. 2+Measure 25 mL of solution containing Pb. 2+ The solution was added to nine 150 mL Erlenmeyer flasks, and then 50 mg of chitosan-ferric oxide-rare earth cerium composite material was added to each flask. The mixtures were shaken at room temperature for 5 min, 10 min, 15 min, 20 min, 30 min, 45 min, 60 min, 90 min, and 120 min, respectively. 25 mL of the solution containing Pb was then measured from each flask. 2+ The solution was added to an Erlenmeyer flask, followed by 50 mg of chitosan-ferric oxide composite material. The mixture was shaken at room temperature for 5 min, 10 min, 15 min, 20 min, 30 min, 45 min, 60 min, 90 min, and 120 min. After shaking, the mixture was filtered. The absorbance of the filtrate was measured after dilution to compare with the standard curve. Based on the obtained data, the adsorption rate and adsorption capacity were calculated to comprehensively evaluate the effect of adsorption time on the adsorption effect and compare the adsorption effects of the two methods under the same conditions.

[0056] according to Figure 7 As shown, the chitosan-iron tetroxide-rare earth cerium composite material has a positive effect on Pb. 2+ The adsorption capacity of the chitosan-ferric oxide composite material increased with time, reaching a peak at 90 minutes. Further increases in adsorption time led to a decrease in adsorption capacity, indicating that 90 minutes was the critical time point for adsorption saturation. Therefore, the optimal adsorption time was determined to be 90 minutes. The chitosan-ferric oxide-rare earth cerium composite material, on the other hand, reached its maximum adsorption capacity at 60 minutes, after which the adsorption capacity decreased, indicating that its optimal adsorption time was 60 minutes. Comparative analysis showed that the chitosan-ferric oxide-rare earth cerium composite material exhibited better adsorption capacity for Pb. 2+ The adsorption effect is better than that of chitosan-iron oxide composite material.

[0057] ③ The effect of adsorbent dosage on adsorption performance: 25 mL of Pb-containing solution with pH 5 and an initial concentration of 75 mg / L was added. 2+ The solution (measured concentration 74.35 mg / L) was added to a 150 mL Erlenmeyer flask, and 5 mg, 10 mg, 15 mg, 25 mg, 50 mg, 75 mg, 100 mg, 125 mg, and 150 mg of chitosan-ferric oxide-rare earth cerium composite material were added respectively. After shaking for 90 min, the solution was filtered and 25 mL of the filtrate with an initial concentration of 75 mg / L Pb at pH 5 was taken. 2+ After adding the solution to the conical flask, 5 mg, 10 mg, 15 mg, 25 mg, 50 mg, 75 mg, 100 mg, 125 mg, and 150 mg of chitosan-ferric oxide composite material were added to each flask, respectively. The mixture was shaken for 60 min and then filtered. Pb was then determined. 2+Concentration, and calculate adsorption rate and adsorption amount. Compare the effects of chitosan-ferric oxide composite material and chitosan-ferric oxide-rare earth cerium composite material dosage on Pb. 2+ The effect of adsorption.

[0058] Depend on Figure 8 It is known that, under constant conditions, the adsorption capacity of the chitosan-ferric oxide-rare earth cerium composite material reaches its maximum at a dosage of 50 mg. Further increases in adsorbent dosage result in a decrease in adsorption capacity; therefore, the optimal adsorbent dosage is determined to be 50 mg. The adsorption capacity of the chitosan-ferric oxide composite material reaches its maximum at a dosage of 25 mg, and the optimal adsorbent dosage is also determined to be 25 mg.

[0059] ④ Chitosan-Fe3O4-Rare Earth Cerium Composite Material for Pb 2+ Adsorption isotherm study: Prepare 25 mL of Pb at pH=5 concentrations of 15 mg / L, 25 mg / L, 40 mg / L, 50 mg / L, 60 mg / L, 75 mg / L, 80 mg / L, and 100 mg / L, respectively. 2+ An ionic solution was added to a 150 mL Erlenmeyer flask. At temperatures of 25℃, 35℃, and 45℃, 50 mg of a chitosan-ferric oxide-rare earth cerium composite material was added. After shaking for 90 min, the mixture was filtered, and the Pb content of the filtrate was determined. 2+ Concentration, and calculate its adsorption amount and adsorption rate.

[0060] Figure 9 The study demonstrated the effect of chitosan-ferric oxide-rare earth cerium composite material on Pb at different temperatures of 25℃, 35℃, and 45℃. 2+ The relationship between adsorption performance and solution concentration was investigated. The curve shows that, within the concentration range of 0 mg / L to 125 mg / L, the adsorption capacity increases with the concentration of Pb in the solution. 2+ The adsorption capacity increases with increasing concentration. When the solution concentration is <75 mg / L, the growth trend of adsorption capacity tends to be gradual. When the concentration is >75 mg / L, the effect of temperature on Pb increases. 2+ The effect of temperature on the adsorption capacity was not significant. The adsorption capacity reached its maximum at a solution concentration of 125 mg / L. Overall, when the solution concentration was <75 mg / L, temperature had little effect on the adsorption of Pb. 2+ The effect is not significant. When the concentration is >75 mg / L, the optimal adsorption temperature is 35℃ and the optimal adsorption concentration is 125 mg / L.

[0061] ⑤ Chitosan-Fe3O4-Rare Earth Cerium Composite Material for Pb 2+ Fitting the isothermal adsorption model: Adsorption isotherms: Adsorption equilibrium at temperatures of 25, 35, and 45 °C was analyzed using Langmuir and Freundlich models.

[0062] Langmuir model expression: .

[0063] in, C e It is the equilibrium concentration (mg / L) of heavy metal ions in the solution. q e It is the adsorption capacity (mg·g) -1 ), K L It is the Langmuir adsorption equation constant (L·mg) -1 ), q m It is the maximum adsorption capacity (mg / L).

[0064] Freundlich model expression: .

[0065] Among them, K F denoted by Freundlich constant, and n represents the adsorption strength constant (the larger the value of n, the easier the adsorption process is).

[0066] Pb 2+ Solutions of different concentrations (15 mg / L, 25 mg / L, 40 mg / L, 50 mg / L, 60 mg / L, 75 mg / L, 80 mg / L, and 100 mg / L) were prepared. 50 mg of chitosan-ferric oxide-rare earth cerium composite material was added to each solution, and the solutions were shaken at 25℃, 35℃, and 45℃ for 90 min. Adsorption data were processed, and the Langmuir isotherm adsorption model and the Freundlich isotherm adsorption model were used to fit the data.

[0067] Table 1 shows the effect of chitosan-ferric oxide-rare earth cerium composite material on Pb in Example 1. 2+ Parameter table of Langmuir adsorption isotherm model Depend on Figure 10 Table 1 shows that RL of the Langmuir model at three temperatures 2 All values ​​are greater than 0.9, indicating that the adsorption at this point conforms to monolayer chemisorption, and the adsorption affinity constant (K) is high. L The effect increases with increasing temperature, mainly due to the interaction between surface active sites and Pb. 2+ The chemical complexation process is involved. The theoretical maximum adsorption capacity at 35℃ is... q m =62.6174) is slightly higher than the maximum adsorption capacity at 45℃, mainly because the high temperature causes some active sites to become inactive.

[0068] Table 2 shows the effect of chitosan-ferric oxide composite material on Pb in Comparative Example 1.2+ Parameter table of Freundlich adsorption isotherm model Depend on Figure 11 Table 2 shows that, based on the Freundlich adsorption isotherm fitting results, the correlation coefficients R0 at 25℃, 35℃, and 45℃ are... 2 All values ​​were less than 0.8, indicating that the Freundlich model effectively controlled the adsorption of Pb by the chitosan-ferric oxide-rare earth cerium composite material. 2+ The process fit is insufficient.

[0069] It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range, as well as any value between the two endpoints, can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described here to avoid redundancy. Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this invention.

Claims

1. A chitosan-iron(II) oxide-rare earth cerium composite material, characterized in that, The chitosan-iron oxide-rare earth cerium composite material is composed of a matrix skeleton chitosan, a magnetic component iron oxide, and a cerium-containing structural modification component. The chitosan-iron tetroxide-rare earth cerium composite material is distributed in an irregular block shape, and cerium-containing particles are distributed on the surface. The iron oxide is generated in situ and dispersed in the chitosan matrix framework, and the cerium-containing structural modification component binds to the hydroxyl, amino and amide groups on the chitosan molecular chain through coordination.

2. The chitosan-iron tetroxide-rare earth cerium composite material according to claim 1, characterized in that, The cerium-containing structural modification component is a mixture of cerium oxide and cerium hydroxide.

3. A method for preparing the chitosan-ferric oxide-rare earth cerium composite material according to claim 1, characterized in that, Includes the following steps: Chitosan was dissolved in water containing glacial acetic acid to obtain a chitosan solution; A mixed solution of metal salts is obtained by dissolving soluble ferrous salts, soluble ferric salts, and soluble cerium salts together in water. When a mixed solution of metal salts is added to a chitosan solution, the metal ions in the mixed solution undergo a coordination reaction with the amino and hydroxyl groups of chitosan to obtain a chitosan-metal ion complex solution. Chitosan-metal ion complex solution was added dropwise to sodium tripolyphosphate aqueous solution. The polyvalent phosphate in sodium tripolyphosphate ion crosslinked with the protonated amino group of chitosan through electrostatic interaction to form a three-dimensional network structure. At the same time, the phosphate group coordinated with the metal ion in chitosan-metal ion complex to fix the metal ion in the three-dimensional network, thus obtaining the crosslinked product. The cross-linking product was placed in an alkaline solution for precipitation. During the precipitation reaction, Fe in the cross-linking product... 2+ and Fe 3+ With OH - Combined, it undergoes heating and dehydration to form Fe3O4; simultaneously, Ce... 3+ With OH - By combining the formation of cerium hydroxide precipitate and partially converting it into cerium oxide, a chitosan-iron tetroxide-rare earth cerium composite material is obtained.

4. The preparation method according to claim 3, characterized in that, The mass ratio of chitosan, soluble ferric salt, soluble ferrous salt and soluble cerium salt is 1:1.2~1.5:0.9~1.1:0.15~0.

25.

5. The preparation method according to claim 3, characterized in that, The mass ratio of chitosan to sodium tripolyphosphate is 1:2.5~3.

6. The preparation method according to claim 3, characterized in that, The conditions for the crosslinking reaction are: stirring at room temperature for 30 to 40 minutes.

7. The preparation method according to claim 3, characterized in that, The precipitation reaction conditions are: stirring at 90℃~100℃ for 100min~150min.

8. The application of the chitosan-iron tetroxide-rare earth cerium composite material according to claim 1 in the preparation of heavy metal ion adsorbents.

9. The application according to claim 8, characterized in that, Application method: Chitosan-Fe3O4-Rare Earth Cerium composite material was added to a Pb-containing... 2+ Adsorption occurs in aqueous solutions; Among them, chitosan-iron tetroxide-rare earth cerium composite material and Pb-containing 2+ The aqueous solution has a mass-to-volume ratio of 5 mg to 150 mg: 25 mL and contains Pb. 2+ In aqueous solution, Pb 2+ The mass concentration is 15 mg / L to 150 mg / L.

10. The application according to claim 8, characterized in that, The adsorption conditions are: containing Pb 2+ The pH value of the aqueous solution is 3~6, ​​and it is adsorbed at 25℃~45℃ for 5min~120min.

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